The subject of the invention is a catalytic method for transformation of polyolefine wastes into hydrocarbon products, e.g. gasoline, diesel oil and crude oil, and a plant for carrying thereof.
A development of the production of polyolefines and their use in almost every line of life causes a consequent increase of related wastes, collected in the dumps, where they take big space relatively to their weight.
A chemical resistance of polyolefins makes them stable for hundreds of years, while they do not yield to destruction, being, a particularly burdensome contamination of the environment. A problem of mating polyolefin wastes productive is at present the matter of a special priority and is a very important element of a natural environment protection.
The hitherto used methods, such as combustion and gasification are generating more problems than they solve.
Till now they are the most expensive methods of utilisation of plastic wastes and all probes of making them less expensive result with an ecological catastrophe. The said situation causes, the countries taking care of ecology to not allow combustion of plastic wastes.
There are known some methods of a thermical decomposition of polyolefins to hydrocarbons in the range of temperatures between 650-850xc2x0 C. Also there are disclosed the methods combining a high-temperature pyrolysis with consequent catalytic conversion of pyrolytic products to gasoline, diesel oil and crude oil. In the known methods catalysts were used in a form of zeolites, as it has been described in the patent U.S. Pat. No. 4,016,218. The most popular is the use of zeolite ZMS-5 hydrogen form, as known from the patent U.S. Pat. No. 3,702,886. The use of other zeolites, e.q. ZMS-11 (U.S. Pat. No. 3,709,979), ZMS-12 (U.S. Pat. No. 3,832,449), ZMS-23 (U.S. 4,076,842), ZMS-35 (U.S. Pat. No. 4,016,245) and ZMS-48 (U.S. Pat. No. 4375573) is also disclosed. In known and used methods catalysts in a form of zeolites with metal atoms, e.g. platinum are applied also. The basic imperfection of zeolite-type catalysts is their sensitivity to hydrochloride, which causes destruction of a catalyst in concentrations above 200 ppm in a product. Considering the fact, plastic wastes always contain poly/vinyl chloride/, the application of expensive zeolite-type catalysts is economically disadvantegeous.
The American patent description No U.S. Pat. No. 4,584,421 and European patent application NO. 0276081 A2 disclose a thermal decomposition of polyolefin and a catalytic process of products conversion using zeolites. However in that method also chlorine containing polymers have to be selected and separated, which operation makes the whole process unprofitable.
The German patent publication No. DE-A-196 41 743 relates to a method of converting polyolefin waste into hydrocarbons, where the polyolefin waste is treated at temperatures of 180-620xc2x0 C., preferably 300-450xc2x0 C. in the presence of a heavy metal silicate used as a catalyst in amount of up tp 30% by weight, based on the polyolefin waste.
The methods specified above enabled obtaining hydrocarbons with the yield of 60-94%, and the obtained hydrocarbons comprised mainly chains up to C39. Besides the above, a product contained a big share of gaseous substances, which caused a frequent breaks of a process and forced cleaning of the reactor, disturbing and interrupting a continous operation between the maintenance overhauls. The reactors used in the known methods for carrying the reaction had usually a shape of typical chemical reactor in a form of a cylindrical tank, provided with a dosing system, heating system and a low-speed mixer, preventing deposition of the reaction mixture. An analysis of the information material concerning a prior act allowed a conclusion, that an ideal technological solution is a method of polyolefin decomposition at low temperatures in one-step process, carried in a liquid phase of molten polymer, while the used catalyst is hydrochloridexe2x80x94resistance and not expensive.
The above aim is reached in the method according to the invention, using cements as a catalyst. Moreover, it has been found, heavy metals resonates are resistant to hydrochlorine and are the ideal catalysts for breaking C-C bonds in polyolefine chains at low temperatures.